When I bought the truck it had the exhaust on it. I would have never cut off the cat but I'm not throwing any CEL from it. Only from the EGR while cruising but eventually it goes away. Also I was curious of any of you have a problem with the mds being touchy. As in I'll cruise down ther interstate around 70mph and it will kick off with the slightest touch of the throttle, it almost doesn't even wanna kick on.

 

I don't have MDS ('04) thank God and 'Dog has his turned off with his Superchips tuner. If I'm not mistaken the Diablo lets you turn it off as well...

 

Yea it has the option to turn it off, but does it make a noticeable difference on gas mileage?

 

With my Superchips and altered trans shifts I get 12-13 city and 16hwy and thats with MDS disabled. I get a consistent 14 around town(45mph roads)

When I had diablo with mds disabled I was only getting 11city and 15-16highway

Overall, yeah, I lost 1mpg on the highway with it disabled. But I actually gained in the city with it disabled plus the response is lightning fast along with the power. MDS did not kick off instantly(milliseconds they claim) and then the downshift was delayed, although Diablo does support partial dowshift alterations. It's with the Partial upshifts Superchips is well worth it. Click on my sig for the link and info.
My truck would kick on MDS and then the truck would slow down, then kick out mds so it could catch back up to speed. Very annoying and not worth the 1mpg IMO. A truck this size around hilly areas it's useless.

 

That's exactly what mine does is slow down with mds on highway and kick off so it can get back up to speed. I don't plan on changing programmers I don't really have extra money to go out and spend on it I just ****** up stuff when I get a real good deal so my plans are to take and get it custom tuned by my local racing shop. I'll do what all has been mentioned aswell. I had always thought flowmaster was a pretty good performance exhaust guess that was wrong lol.

 

I have an 08 1500 4x4 QC with ds 87 octane tune, s&b C.A.I., magnaflow 12259 muffler, I can get in the upper 17's on the highway 14 to 15 in the city, also what octane are you running, I was running 87, but after reading on here I only run 89, it helped alittle.

 

A lot of guys when they get into performance, they disable the MDS.

 

I'm sorry but I find 14-15 city a little hard to believe on a QC 4x4 who runs 87 (especially an 87 octane tune which I hear is terrible). If you're getting those numbers off the overhead then you're fooling yourself